Fig. 13-1 Figure 13.1 What accounts for family resemblance?

0.5 mm Parent Bud (a) Hydra (b) Redwoods Fig. 13-2 Figure 13.2 Asexual reproduction in two multicellular organisms Parent Bud (a) Hydra (b) Redwoods

0.5 mm Parent Bud (a) Hydra Fig. 13-2a Figure 13.2 Asexual reproduction in two multicellular organisms Parent Bud (a) Hydra

Fig. 13-2b Figure 13.2 Asexual reproduction in two multicellular organisms (b) Redwoods

Figure 13.3 Preparing a karyotype APPLICATION Figure 13.3 Preparing a karyotype TECHNIQUE 5 µm Pair of homologous replicated chromosomes Centromere Sister chromatids Metaphase chromosome

Fig. 13-3a APPLICATION Figure 13.3 Preparing a karyotype

TECHNIQUE 5 µm Pair of homologous replicated chromosomes Centromere Fig. 13-3b TECHNIQUE 5 µm Pair of homologous replicated chromosomes Centromere Figure 13.3 Preparing a karyotype Sister chromatids Metaphase chromosome

Key Maternal set of chromosomes (n = 3) 2n = 6 Paternal set of Fig. 13-4 Key Maternal set of chromosomes (n = 3) 2n = 6 Paternal set of chromosomes (n = 3) Two sister chromatids of one replicated chromosome Figure 13.4 Describing chromosomes Centromere Two nonsister chromatids in a homologous pair Pair of homologous chromosomes (one from each set)

Multicellular diploid adults (2n = 46) Fig. 13-5 Key Haploid gametes (n = 23) Haploid (n) Egg (n) Diploid (2n) Sperm (n) MEIOSIS FERTILIZATION Figure 13.5 The human life cycle Ovary Testis Diploid zygote (2n = 46) Mitosis and development Multicellular diploid adults (2n = 46)

Figure 13.6 Three types of sexual life cycles Key Haploid (n) Haploid unicellular or multicellular organism Diploid (2n) Haploid multi- cellular organism (gametophyte) n Gametes n n Mitosis n Mitosis Mitosis n Mitosis n n n n n MEIOSIS FERTILIZATION Spores n n Figure 13.6 Three types of sexual life cycles Gametes Gametes n MEIOSIS FERTILIZATION Zygote MEIOSIS FERTILIZATION 2n 2n 2n 2n Diploid multicellular organism Zygote Diploid multicellular organism (sporophyte) 2n Mitosis Mitosis Zygote (a) Animals (b) Plants and some algae (c) Most fungi and some protists

Key Haploid (n) Diploid (2n) Gametes n n n MEIOSIS FERTILIZATION Fig. 13-6a Key Haploid (n) Diploid (2n) Gametes n n n MEIOSIS FERTILIZATION Figure 13.6a Three types of sexual life cycles—animals Zygote 2n 2n Diploid multicellular organism Mitosis (a) Animals

(b) Plants and some algae Fig. 13-6b Key Haploid (n) Haploid multi- cellular organism (gametophyte) Diploid (2n) Mitosis Mitosis n n n n n Spores Gametes Figure 13.6b Three types of sexual life cycles—plants and some algae MEIOSIS FERTILIZATION 2n 2n Zygote Diploid multicellular organism (sporophyte) Mitosis (b) Plants and some algae

Haploid unicellular or multicellular organism Diploid (2n) Fig. 13-6c Key Haploid (n) Haploid unicellular or multicellular organism Diploid (2n) Mitosis Mitosis n n n n Figure 13.6c Three types of sexual life cycles—most fungi and some protists Gametes n MEIOSIS FERTILIZATION 2n Zygote (c) Most fungi and some protists

Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number

Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Meiosis I 1 Homologous chromosomes separate Haploid cells with replicated chromosomes

Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Interphase Homologous pair of chromosomes in diploid parent cell Chromosomes replicate Homologous pair of replicated chromosomes Sister chromatids Diploid cell with replicated chromosomes Figure 13.7 Overview of meiosis: how meiosis reduces chromosome number Meiosis I 1 Homologous chromosomes separate Haploid cells with replicated chromosomes Meiosis II 2 Sister chromatids separate Haploid cells with unreplicated chromosomes

Figure 13.8 The meiotic division of an animal cell Prophase I Metaphase I Anaphase I Telophase I and Cytokinesis Prophase II Metaphase II Anaphase II Telophase II and Cytokinesis Centrosome (with centriole pair) Sister chromatids remain attached Centromere (with kinetochore) Sister chromatids Chiasmata Spindle Metaphase plate Figure 13.8 The meiotic division of an animal cell Sister chromatids separate Haploid daughter cells forming Homologous chromosomes Homologous chromosomes separate Cleavage furrow Fragments of nuclear envelope Microtubule attached to kinetochore

Prophase I Metaphase I Anaphase I Centrosome (with centriole pair) Fig. 13-8a Telophase I and Cytokinesis Prophase I Metaphase I Anaphase I Centrosome (with centriole pair) Sister chromatids remain attached Centromere (with kinetochore) Sister chromatids Chiasmata Spindle Metaphase plate Figure 13.8 The meiotic division of an animal cell Cleavage furrow Homologous chromosomes Homologous chromosomes separate Fragments of nuclear envelope Microtubule attached to kinetochore

Prophase I Metaphase I Centrosome (with centriole pair) Centromere Fig. 13-8b Prophase I Metaphase I Centrosome (with centriole pair) Centromere (with kinetochore) Sister chromatids Chiasmata Spindle Metaphase plate Figure 13.8 The meiotic division of an animal cell Homologous chromosomes Fragments of nuclear envelope Microtubule attached to kinetochore

Telophase I and Cytokinesis Fig. 13-8c Telophase I and Cytokinesis Anaphase I Sister chromatids remain attached Figure 13.8 The meiotic division of an animal cell Homologous chromosomes separate Cleavage furrow

Telophase II and Cytokinesis Fig. 13-8d Telophase II and Cytokinesis Prophase II Metaphase II Anaphase II Figure 13.8 The meiotic division of an animal cell Sister chromatids separate Haploid daughter cells forming

Prophase II Metaphase II Fig. 13-8e Figure 13.8 The meiotic division of an animal cell

Telephase II and Cytokinesis Fig. 13-8f Telephase II and Cytokinesis Anaphase II Figure 13.8 The meiotic division of an animal cell Sister chromatids separate Haploid daughter cells forming

Figure 13.9 A comparison of mitosis and meiosis in diploid cells Parent cell Chiasma Chromosome replication Chromosome replication Prophase Prophase I Homologous chromosome pair Replicated chromosome 2n = 6 Metaphase Metaphase I Anaphase Anaphase I Telophase Telophase I Haploid Figure 13.9 A comparison of mitosis and meiosis in diploid cells n = 3 Daughter cells of meiosis I 2n 2n MEIOSIS II Daughter cells of mitosis n n n n Daughter cells of meiosis II SUMMARY Property Mitosis Meiosis DNA replication Occurs during interphase before mitosis begins Occurs during interphase before meiosis I begins Number of divisions One, including prophase, metaphase, anahase, and telophase Two, each including prophase, metaphase, anaphase, and telophase Synapsis of homologous chromosomes Does not occur Occurs during prophase I along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion Number of daughter cells and genetic composition Two, each diploid (2n) and genetically identical to the parent cell Four, each haploid (n), containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other Role in the animal body Enables multicellular adult to arise from zygote; produces cells for growth, repair, and, in some species, asexual reproduction Produces gametes; reduces number of chromosomes by half and introduces genetic variability amoung the gametes

Replicated chromosome Fig. 13-9a MITOSIS MEIOSIS MEIOSIS I Parent cell Chiasma Chromosome replication Chromosome replication Prophase Prophase I Homologous chromosome pair 2n = 6 Replicated chromosome Metaphase Metaphase I Figure 13.9 A comparison of mitosis and meiosis in diploid cells Anaphase Telophase Anaphase I Telophase I Haploid n = 3 Daughter cells of meiosis I 2n 2n MEIOSIS II Daughter cells of mitosis n n n n Daughter cells of meiosis II

Figure 13.9 A comparison of mitosis and meiosis in diploid cells Fig. 13-9b SUMMARY Property Mitosis Meiosis DNA replication Occurs during interphase before mitosis begins Occurs during interphase before meiosis I begins Number of divisions One, including prophase, metaphase, anaphase, and telophase Two, each including prophase, metaphase, anaphase, and telophase Synapsis of homologous chromosomes Figure 13.9 A comparison of mitosis and meiosis in diploid cells Does not occur Occurs during prophase I along with crossing over between nonsister chromatids; resulting chiasmata hold pairs together due to sister chromatid cohesion Number of daughter cells and genetic composition Two, each diploid (2n) and genetically identical to the parent cell Four, each haploid (n), containing half as many chromosomes as the parent cell; genetically different from the parent cell and from each other Role in the animal body Enables multicellular adult to arise from zygote; produces cells for growth, repair, and, in some species, asexual reproduction Produces gametes; reduces number of chromosomes by half and introduces genetic variability among the gametes

Two of three possible arrange- ments of labeled chromosomes Fig. 13-10 EXPERIMENT Shugoshin+ (normal)+ Shugoshin– Spore case Fluorescent label Metaphase I Anaphase I Metaphase II OR Anaphase II ? ? ? ? Figure 13.10 What prevents the separation of sister chromatids at anaphase I of meiosis? Mature spores ? ? ? ? Spore Two of three possible arrange- ments of labeled chromosomes RESULTS 100 80 Spore cases (%) 60 40 20 Shugoshin+ Shugoshin–

Two of three possible arrange- ments of labeled chromosomes Fig. 13-10a EXPERIMENT Shugoshin+ (normal) Shugoshin– Spore case Fluorescent label Metaphase I Anaphase I Figure 13.10 What prevents the separation of sister chromatids at anaphase I of meiosis? Metaphase II OR Anaphase II ? ? ? ? Mature spores ? ? ? ? Spore Two of three possible arrange- ments of labeled chromosomes

RESULTS 100 80 60 Spore cases (%) 40 20 Shugoshin+ Shugoshin– Fig. 13-10b RESULTS 100 80 Figure 13.10 What prevents the separation of sister chromatids at anaphase I of meiosis? 60 Spore cases (%) 40 20 Shugoshin+ Shugoshin–

Possibility 2 Possibility 1 Two equally probable arrangements of Fig. 13-11-1 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Figure 13.11 The independent assortment of homologous chromosomes in meiosis

Possibility 2 Possibility 1 Two equally probable arrangements of Fig. 13-11-2 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Figure 13.11 The independent assortment of homologous chromosomes in meiosis Metaphase II

Possibility 1 Possibility 2 Two equally probable arrangements of Fig. 13-11-3 Possibility 1 Possibility 2 Two equally probable arrangements of chromosomes at metaphase I Figure 13.11 The independent assortment of homologous chromosomes in meiosis Metaphase II Daughter cells Combination 1 Combination 2 Combination 3 Combination 4

Prophase I Nonsister of meiosis chromatids held together Fig. 13-12-1 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Figure 13.12 The results of crossing over during meiosis

Prophase I Nonsister of meiosis chromatids held together Fig. 13-12-2 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Figure 13.12 The results of crossing over during meiosis

Prophase I Nonsister of meiosis chromatids held together Fig. 13-12-3 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Figure 13.12 The results of crossing over during meiosis Anaphase I

Prophase I Nonsister of meiosis chromatids held together Fig. 13-12-4 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Figure 13.12 The results of crossing over during meiosis Anaphase I Anaphase II

Recombinant chromosomes Fig. 13-12-5 Prophase I of meiosis Nonsister chromatids held together during synapsis Pair of homologs Chiasma Centromere TEM Figure 13.12 The results of crossing over during meiosis Anaphase I Anaphase II Daughter cells Recombinant chromosomes

Prophase I: Each homologous pair undergoes Fig. 13-UN1 Prophase I: Each homologous pair undergoes synapsis and crossing over between nonsister chromatids. Metaphase I: Chromosomes line up as homolo- gous pairs on the metaphase plate. Anaphase I: Homologs separate from each other; sister chromatids remain joined at the centromere.

Fig. 13-UN2 F H

Fig. 13-UN3

Fig. 13-UN4

You should now be able to: Distinguish between the following terms: somatic cell and gamete; autosome and sex chromosomes; haploid and diploid Describe the events that characterize each phase of meiosis Describe three events that occur during meiosis I but not mitosis Name and explain the three events that contribute to genetic variation in sexually reproducing organisms Copyright © 2008 Pearson Education Inc., publishing as Pearson Benjamin Cummings